Mobile computing devices and related display technologies are well known. A mobile computing device could include or cooperate with a head mounted display unit that provides a physically compact display element that is held within close proximity to the user's eye. A head mounted display unit could be used to provide image content to the user in situations where it would be impractical to carry or otherwise utilize a traditional display monitor. A head mounted display unit can provide a very small physical display element that appears to the user as a virtual image of a full size video monitor. Due to their mobility, usability, and portability, head mounted display units are becoming increasingly popular in certain applications (e.g., advanced military weapons platforms, virtual reality systems, service, construction, and architecture). A virtual image provided by a head mounted display unit can also be employed as a graphical user interface for a mobile computing device, cooperating with voice commands and/or physical user interface features.